Method for producing a porous carbon article and an article produced thereby

ABSTRACT

A workpiece with transport porosity is formed. Nanopores are formed in the workpiece by a thermochemical treatment. The workpiece is formed as a rigid carbonaceous skeleton containing in its structure particles of one or more carbides, being selected and arranged in order to provide predetermined nanopore sizes, a predetermined volume of nanopores and a predetermined distribution of nanopores within the volume of the article dependent on its intended use.

TECHNICAL FIELD

The present invention relates to a method for producing a porous carbonarticle comprising the steps of forming a workpiece with transportporosity and forming nanopores in said workpiece by thermochemicaltreatment. The invention also relates to an article produced by saidmethod.

BACKGROUND TO THE INVENTION

From “Application of tubular articles in cryoadsorption pumps//Carbonadsorbents and their application in industries.”, Breslavets K. S et al,Moscow, Science publishers, 1983, p. 243, a method for producing aporous carbon article is known. The method comprises a step of formingor extrusion of a paste consisting of silicon carbide powder andcommercial synthetic resins as a binder in order to produce a desiredarticle. In this case, transport porosity of the material is formed withpore size above 100 nm. Then a carbonization in an inert medium iscarried out in order to strengthen the article and make its structuremore uniform. Further the article undergoes a thermochemical treatmentby chlorine at 900–1000° C. for transformation of carbide into carbon.In this step, in the volume of the article a nanoporous structure withpore size less than 10 nm is formed.

Use of a polymeric resin as a binder is an obstacle for obtaining highmechanical strength, because of the low mechanical strength ofcarbonized resin. Resin destruction accompanies formation of carbonwhich also takes part in the process of forming nanoporosity, but thesize of this porosity is practically uncontrollable. As a result, it isimpossible to produce materials with predetermined adsorption propertieswith the known method.

An article produced by means of the known method is a carbon materialbinded with products of resin carbonization with porosity of 65 to 75vol % in this case, a part of the pores, 30–32 vol % are transport poreshaving size greater than 100 nm, while other pores have size less than10 nm.

Application of articles obtained by the known method is restrictedbecause it gives no possibility to obtain controllable size of pores aswell as controllable volumetric content of both transport porosity andnanoporosity.

A number of so called activated carbons with a high content ofnanoporosity is known, but the pore size distribution for thesematerials is very wide and uncontrolled, c.f. “Carbon”, John Wiley &Son, N.Y. 1988,USA.

It is thus a need for a method in which the porosities of a porouscarbon material which comprise two types of pores can be controlled. Thetwo types are pores of a size less than 10 nm providing adsorptionability and pores of a size greater than 100 nm providing transportationof a component to the pores taking active part in the adsorptionprocess. Articles produced by such a method can be used in differentfields of technology connected with adsorption and absorption processes,such as selective absorption of a component from a liquid or gas,electrochemical electrodes, in medicine technologies, etc.

The object of the present invention is to make it possible to producecarbon porous articles with predetermined transport porosity andpredetermined nanopore sizes, volume and distribution throughout thevolume of the article.

SUMMARY OF THE INVENTION

This object is achieved by a method for producing a porous carbonarticle comprising the steps of formation of one or more carbide powdersto an intermediate body with transport pores, i.e. pores having a sizelarger than 100 nm, by shaping, characterised by the further steps of,selecting the one or more carbide powders on the basis of dependence ofspecified nanopore size on physical and chemical constants of thecarbides using the relationship;X=Z*(1−R)/Rwhere

-   -   X=specified size of nanopores, nm;    -   Z=0.65–0.75 nm;    -   R=νM_(c)ρ_(k)/M_(k)ρ_(c)        where    -   M_(c)—molecular mass of carbon, g/mole;    -   M_(k)—molecular mass of carbide, g/mole;    -   ρ_(k)—density of carbide, g/ccm;    -   ρ_(c)—density of carbon, g/ccm;        ν—number of carbon atoms in carbide molecule, heat treating the        intermediate body in a medium of gaseous hydrocarbon or        hydrocarbon mixtures at a temperature exceeding the        decomposition temperature for the hydrocarbon or hydrocarbons        until the mass of the intermediate body has increased at least        3% thereby creating a workpiece in the form of a rigid        carbonaceous skeleton,        thereafter thermochemically treating the work piece in a medium        of gaseous halogens        to provide predetermined nanopore sizes, i.e the pores have a        size less than 10 nm, a predetermined volume of nanopores, and a        predetermined distribution of nanopores within the volume of the        article, the carbides used forming carbons having a slot-like        structure. By this method materials having controlled and        predetermined nanopores, an optimal ratio between volumes of        transport pores and nanopores, high mechanical strength and        complicated shapes can be produced.

In a preferred embodiment elements from III, IV, V or VI group ofMendeleyv's Periodic system are selected as carbon precursor.

The formulation of carbide particle mixture is chosen in dependence ofdesired distribution of nanopores by sizes using the relationship;Ψ_(i) =K _(i)φ_(i) /ΣK _(i)φ_(i)where

-   -   Ψ_(i)—volumetric part of nanopores with size x_(i) in total        volume of nanopores;    -   φ_(i)—volumetric part of i-th carbide in particle mixture;    -   n—number of carbides;        K _(i)=1−νM _(c)ρ_(ki) /M _(ki)ρ_(c)        where    -   M_(c)—molecular mass of carbon, g/mole;    -   M_(ki)—molecular mass of it-h carbide, g/mole;    -   ρ_(ki)—density of it-h carbide, g/ccm;    -   ρ_(c)—density of carbon, g/ccm;    -   ν—number of carbon atoms in carbide molecule.

The intermediate body is formed with a porosity of 30–70 vol %,preferably 35–50 vol %, the porosity being determined with the followingrelationship;ε₀=[1−ν_(np) /ΣK _(i)φ_(i)]*100where

-   -   ε₀—porosity of intermediate body, vol %;    -   φ_(i)—volumetric part of i-th carbide in particle mixture;    -   ν_(np)—predetermined volumetric part of nanopores in final        article;        K _(i)=1−νM _(c)ρ_(ki) /M _(ki)ρ_(c)        where    -   M_(c)—molecular mass of carbon, g/mole;    -   M_(ki)—molecular mass of it-h carbide, g/mole;    -   ρ_(ki)—density of it-h carbide, g/ccm;    -   ρ_(c)—density of carbon, g/ccm;    -   ν—number of carbon atoms in carbide molecule.

The treatment in a medium of gaseous hydrocarbon or hydrocarbon iscarried out until the mass of the intermediate body has changedaccording to the following relationship;Δm=Q(ε₀ −v _(tr))/(1−ε₀)where

-   -   Δm—relative change of intermediate body mass, g/g;    -   ε₀—porosity of intermediate body, vol %;    -   v_(tr)—predetermined volumetric content of transport pores, vol        %;        Q=ρ _(c)/ρ_(mix)        Where    -   ρ_(c)=density of carbon, g/ccm;    -   ρ_(mix)=density of carbides mixture, g/ccm;

The intermediate body can be formed by pressing. Other well knownforming methodes, such as slip casting, tape casting or slurry castingand injection moulding can of course also be used. nNatural gas is usedas a mixture of hydrocarbons and the treating in hydrocarbon medium iscarried out at 750–950° C.

Alternatively at least one of the hydrocarbons used during the treatmentof the intermediate body in hydrocarbons medium is selected from thegroup of acetylene, methane, ethane, propane, pentane, hexane, benzeneand their derivatives and the treating in hydrocarbon medium is carriedout at 550–1200° C.

The particles of carbide or carbides of which the intermediate body isformed are arranged uniformly or nonuniformly throughout its volume.

The thermochemical treatment of the workpiece is carried out in a mediumof gaseous halogens at 350–1200° C., preferably chlorine. at 500–1100°C.

The present invention relates also to a porous carbon article havingnanopores, i.e pores having a size less than 10 nm, and transport pores,i.e. pores having a size grater than 100 nm, characterised in that thearticle consists of a rigid carbon skeleton in which at least 3% of itsmass consists of carbon without nanopores.

In an embodiment the article has nanopores of at least two sizes.Furthermore, the volume of nanopores is 15–50% and the volume oftransport pores is 10–55% the nanopores are distributed uniformly ornonuniformly throughout the volume of the article.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will now be described with reference to thefollowing figures, of which;

FIG. 1 shows a table of the properties of materials produced in example1, and

FIG. 2 disclose porosimetry data for the sample of example 1–3.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The method according to the invention comprises the following steps:

1) Forming a workpiece with transport porosity using particles of acarbide or carbides of elements from III, IV, V and VI groups ofMendeleyev's Periodic System, in the form of a rigid carbonaceousskeleton containing in its structure particles of a carbide or carbidesselected from the said groups and arranged in a predetermined orderproviding formation in the subsequent steps desired transport porosityand nanoporosity by sizes, volume and distribution of pores throughoutthe volume of the article;

2) Formation of nanoporosity throughout the volume of a workpieceobtained in the 1st step by thermochemical treatment of the saidworkpiece in gaseous halogens, such as chlorine, at elevatedtemperatures in the range of 350 to 1200° C., preferably 500–1100° C.

Current notions of carbon materials structure point out that nanoporesgenerated during the thermochemical treatment process are formed byordered or disordered graphite planes of carbon, which for simplicitymight be considered as shaped as slots, the width of the latterdepending on type of carbide used for forming of the workpiece withtransport porosity.

These theoretical ideas are in good agreement with experimental datawhich allowed the inventors to disclose the following dependence forcarbon materials having such structure:X=Z*(1−R)/R  (1)where X-predetermined size of nanopores, nm;

-   -   Z—experimental factor established for a number of carbide        structures of elements from III, IV, V and VI groups of        Mendeleyev's Periodic System as 0.65–0.75 nm;        R=νM _(c)ρ_(k) /M _(k)ρ_(c)        where    -   M_(c)—molecular mass of carbon, g/mole;    -   M_(k)—molecular mass of carbide, g/mole;    -   ρ_(K)—density of carbide, g/ccm;    -   ρ_(c)—density of carbon, g/ccm;    -   ν—number of carbon atoms in carbide molecule.

A series of preliminary experiments made it possible to choose anecessary carbide to obtain in practice a predetermined size ofnanopores.

Particles of a chosen carbide (powder) are formed into an intermediatebody with porosity in the range of 30–70 vol % by any known method, e.g.by pressing with or without temporary binder, slip casting, slurrycasting. Final step of forming, which results in production of aworkpiece with a high mechanical strength and a desired transportporosity, is a treating of the intermediate body in a medium of gaseoushydrocarbon or hydrocarbons mixture at a temperature above theirdecomposition temperature.

It is possible to use natural gas and/or at least a hydrocarbon selectedfrom the group comprising acetylene, methane, ethane, propane, pentane,hexane, benzene and their derivatives.

Under these conditions a decomposition of hydrocarbon occurs byreaction;C_(m)H_(n) →mC+^(n)/₂H₂↑  (2)with deposition of the generated pyrocarbon on the surface and in thepores of intermediate body volume.

The specified range of initial porosity is baser on the fact that at aporosity below 30% it is difficult to obtain sufficient volume oftransport pores in the article providing access of adsorptive tonanopores where adsorption process occurs and at a porosity above 70%the article does not possess satisfactory mechanical strength.

The value of 35–50 vol % is preferable because it is easily achieved byany available method of workpiece forming and it assures an optimalrelation between volumes of transport pores and nanopores in thearticle.

The size and distribution of the transport pores can be controlled byselecting appropriate particle sizes and particle distribution. Theamount of possible particle packing due to the forming process will ofcourse also influence the porosity of the work piece.

Calculation of concrete value of intermediate body porosity necessary toobtain a predetermined volume of nanopores, is carried out using thefollowing expression:

$\begin{matrix}{ɛ_{0} = {\left\lbrack {1 - {v_{np}/{\sum\limits_{i - 1}^{n}{K_{i}\varphi_{i}}}}} \right\rbrack \cdot 100}} & (3)\end{matrix}$where

-   -   ε₀—porosity of intermediate body, vol %;    -   φ_(i)—volumetric part of i-th carbide in powder mixture;    -   V_(np)—predetermined volumetric part of nanopores in final        article.        K _(i)=1−νM _(c)ρ_(ki) /M _(ki)ρ_(c)        where    -   M_(c)—molecular mass of carbon, g/mole;    -   M_(ki)—molecular mass of i-th carbide, g/mole;    -   ρ_(c)—density of carbon, g/ccm;    -   ρ_(ki)—density of i-th carbide, g/ccm:    -   ν—number of carbon atoms in carbide molecule;    -   n—number of carbides in the mixture.

Duration of treating in the said medium is controlled by measuring themass of the article. When the mass has changed by at least 3%, thestrength is already sufficient for use of the article as adsorptionelement, capacitor electrode or chromatography membrane, for instance.

The process is usually completed when the mass is changed by 3–20%, thusproviding necessary strength of the article and its transport porosity.Lower and upper limits are determined by use of carbides from saidgroups with different densities.

In practice an experimental expression is used allowing for a given typeof carbide at predetermined strength properties to obtain necessaryvalue of transport porosity which, depending on active agent in thepores, can determine kinetics of the process. This expression is asfollows:Δm=Q(ε₀ −v _(tr))/(1−ε₀)  (4)where

-   -   Δm—relative change of intermediate body mass, g/g;    -   ε₀—porosity of intermediate body, vol %;    -   V_(tr)—predetermined volumetric content of transport pores, vol        %;        Q=ρ _(c)/ρ_(mix)        where    -   ρ_(c)—density of carbon, g/ccm:    -   ρ_(mix)—density of carbides mixture, g/ccm.

In order to obtain an article with nanopores of different sizes, makingit possible to realize selective filtration and adsorption, more thanone carbide should be chosen. For this goal the formula (1) or anexperimentally determined pore size value is used and the followingdependence, confirmed experimentally, allows an determination of thepart of each carbide in the mixture necessary to manufacture such anarticle;

$\begin{matrix}{\Psi_{i} = {K_{i}{\varphi_{i}/{\sum\limits_{i = 1}^{n}{K_{i}\varphi_{i}}}}}} & (5)\end{matrix}$where

-   -   ψ_(i)—volumetric part of nanopores with size x_(i) in total        volume of nanopores;    -   φ_(i)—volumetric part of i-th carbide in powder mixture;    -   n—number of carbides;        K_(i)=1−νM _(c)ρ_(ki) /M _(ki)ρ_(c)        where    -   M_(c)—molecular mass of carbon, g/mole;    -   M_(ki)—molecular mass of i-th carbide, g/mole;    -   ρ_(ki)—density of it-h carbide, g/ccm;    -   ρ_(c)—density of carbon, g/ccm;    -   ν—number of carbon atoms in carbide molecule.

In order to obtain a uniform distribution of nanopores throughout thearticle volume a mixture is formed with uniformly distributed powders ofvarious carbides in it (homogeneous mixture); if it is necessary toobtain nanopores distributed throughout the volume in a desired order amixture is prepared by means of any known method with particlesdistributed according to the desired order, e.g. layerwise.

After completed forming, a workpiece is obtained as a rigid carbonaceousskeleton with transport porosity formed in its volume allowing to obtainin the step of thermochemical treatment uniform nanopores of apredetermined size.

In order to form nanoporosity the obtained workpiece is subjected tothermochemnical treatment by chlorine at 500–1100° C. Nanoporosity isformed at removal of volatile chlorides of carbide-forming elements inaccordance with reaction:E _(k)C_(f)+(km/2n)Cl₂ →k/n E _(n)Cl_(m) ↑+fC  (6)where

-   -   E_(k)C_(f)—primary carbide;    -   k, f, n, m—stoichiometric coefficients.

The treatment is carried out until mass change of the workpiece hasstopped.

A finished article produced by the described method has a predeterminedshape and size, and its structure is a porous carbon skeleton withtransport porosity of 10–55% obtained in the step of forming andnanoporosity of 15–50% volume. The article comprises one or severaltypes of nanopores and each type is being characterized with narrowdistribution by size. Carbon content in the skeleton is more than 95 wt%, preferably 99 wt %, i.e., practically, the obtained article consistsof pure carbon and has considerable strength allowing to increase itslife time and expand application range under conditions when shapemaintaining during operation is necessary.

As a result of selecting appropriate carbides and accomplishment offorming under conditions determined beforehand by means of relationshipsestablished by the inventors, a finished article is obtained withnanopore sizes, volume and distribution corresponding to those of theobject of the article operation.

Among possible forming methods to realize the said method pressing, slipcasting, tape casting and slurry casting can be named.

A formed intermediate body is treated in a medium of at least onehydrocarbon selected from the group comprising acetylene, methane,ethane, propane, pentane, hexane, benzene and their derivatives. Whenusing hydrocarbons from the said group an optimal temperature range is550–1200° C., the decomposition temperatures for these hydrocarbonsfalling within this range. It is also possible to use natural gas and inthis case it is expedient to keep temperature in the range of 750–950°C.

A halogenation is carried out just like in the known method, with thetemperature being selected in the range of 350–1200° C., depending onthe nature of initial carbides and the formed volatile halogenides.Under these conditions volatile halogenides of carbide-forming elementsare completely removed out of the article according to a reactionsimilar to reaction (6). However, only halogens and halogenides which donot react with carbon under the prevailing temperature conditions may beused.

The claimed concept is further elucidated with the following examples.

EXAMPLE 1

An example of producing an article in the tablet form with sizes d=20mm, h=5 mm, with nanopore size 0.8 nm and nanopore volume 0.3 ccm/ccmuniformly distributed throughout the article volume, suitable forforming on its surface a double electric layer of high capacitance inelectrolyte solutions.

To produce an article on the basis of beforehand obtained dependence (1)for X=0.8 nm titanium carbide powder was chosen. By substitution of thevalues of molecular mass and density of titanium carbide and carbon(M_(c)=12 g/mole; ρ_(c)=2.2 g/ccm; ρ_(k)=ρ_(TiC)=4.92 g/ccm;M_(k)=M_(TiC)=59.88 g/mole) in the formula (1) the following isobtained:

R=12*4.92/59.88*2.2=0.448, X=Z(1−0.448)/0.448=1.232Z nm;

Thus when Z is in the range of 0.65–0.75, the nanpore size of theproduced carbon materials will be in the range of 0.8–0.92.

In order to obtain the predetermined volume of nanopores (V_(np)=0.3ccm/ccm), prior to pressing a needed porosity of the intermediate bodyis determined by the relationship (3): where φ_(i)=1, n=1, as followsε₀=[1−0.3/(1−0.448)]*100=46%

Amount of TiC powder necessary to produce an intermediate body which hasthe predetermined sizes and the obtained value of porosity is calculatedby the following dependence:m=ρ _(k)(100−ε₀)·V/100where

-   -   V—article volume, V=(πd²/4)*h, ccm;    -   d—workpiece diameter, 2 cm;    -   h—workpiece height, 0.5 cm; hence:        m=4.92(100−46)(3.14*2^(2/)4)*0.5=5.01 g

The needed mass change of the intermediate body during pyrocarbondeposition is calculated by formula (4), assuming a transport porosityof 35 vol %Then, Δm=[0.4476(46−35)/(100−46]*100=9.1%

A mixture is prepared using 5.01 g of TiC powder with a size of theparticles of 20 μm. Ethyl alcohol is added in the amount of 10%, of themass of the mixture. Then, an intermediate body is formed by pressing ona hydrostatic press machine (P-125) at 30±1 Mpa pressure. After thepressing, the intermediate body is dried at 150±10° C. during 1–1.5 houruntil complete removal of temporary binder.

This is followed by pyrocarbon deposition on the intermediate body bymeans of heat treatment in natural gas medium at atmospheric pressure ina quartz continuous reactor at 850° C. during 12 hours until change ofmass by 9.1%.

Then, the sample is chlorinated. The chlorination is carried out in aisothermal quartz reactor at 650° C. during 4 hours. Then a blow-throughof the reactor with argon at a temperature of 800° C. is carried out toremove excessive chlorine out of the reactor zone and the internalsurface of the sample.

Properties of the obtained material are presented in Table 1. From thistable it is evident that the measured peak value of the nanopore sizemeasured by gas porosimetry correspond to the calculated value.

Two articles produced according to Example 1 were saturated with 20% KOHsolution by boiling and placing them in an electrolyte solution (20%KOH). Opposite by sign potential was applied to each of the articles toform a double electric layer in the material nanopore volume. In thiscase the specific electrical capacitance of the double electric layerformed in the material was 37.8 F/g.

Notes:

1) Total volume of pores is determined by hydrostatic method accordingto GOST 473.4–81.

2) Nanopore volume is determined by exsiccator method by adsorption ofbenzene under static conditions, see “Fundamentals of adsorptiontechnology.” Keltsev N. V., Moscow, Chemistry publishers, 1984, p. 33.

3) Transport pore volume is determined by formulaV _(tr) =V _(Σ) −V _(np).

4) Size of nanopores is determined by means of mercury and gasporosimetry (Micromeretics Auto Pore III and Micromeretics ASAP 2010,respectively). Data are shown in FIG. 2. Legend Hg denotes mercuryporosimetry intrusion data, legend BJH denotes gas porosimetrydesorption data analysed by the BJH method, and legend Micro denotes gasporosimetry data analysed by the Horvath-Kawazoe method.

The presented data allows one to draw the conclusion that a new methodfor producing a porous carbon article comprising transport pores andnanopores with controllable sizes and distribution of nanoporesthroughout its volume as well as volumetric content of both types ofporosity has been developed. The articles according to the invention canfind wide application for adsorption and microdosage of substances,purification and separation of cryogenic liquids and gas mixtures, ashigh-porous electrode materials etc. owing to presence of porosity ofdesired sizes.

By the inventive method it is possible to produce nanopore volume andsize or sizes by a mechanism independent from the mechanism forproducing transport porosity in the materials produced, thereby makingit possible to control purposely parameters of their porous structure.At development of adsorption materials, for instance, the followingparameters can be optimized when using the present invention:

1) adaptability to manufacture of devices working components made ofthese materials;

2) optimal relationship between volumes of transport pores and nanoporeswhich provide effective adsorption;

3) mechanical strength;

4) increased heat conductivity allowing to use these materials incryo-adsorption evacuation elements.

Furthermore, the present method, besides the advantages pointed out,allows production of articles of complex shapes, in particular, ofshapes impossible to obtain by any other known method, with minimummachining required. Owing to high mechanical strength the articlesaccording to the invention can be used under conditions demandingmaintenance of their shape.

1. A method for producing a porous carbon article comprising the stepsof: selecting powders of at least one carbide of an element selectedfrom the group consisting of Group III, IV, V and VI of Mendeleyv'sPeriodic System, the at least one carbide having physical and chemicalconstants to obtain a porous carbon article having a desirednanoporosity by calculating using the relationship:X=Z*(1−R)/R where X=specified size of desired nanopores and X≦10 nm;Z=0.65–0.75 nm;R=νM _(c)=ρ_(k) /M _(k)ρ_(c) where M_(c)—molecular mass of carbon,g/mole; M_(k)—molecular mass of the selected carbide, g/mole;ρ_(k)—density of the selected carbide, g/ccm; ρ_(c)—density of carbon,g/ccm; ν—number of carbon atoms in carbide molecule; forming anintermediate body with transport pores having a size larger than 100 nmby shaping the selected powders; heat treating the intermediate body ina medium of gaseous hydrocarbon or hydrocarbon mixtures at a temperatureexceeding the decomposition temperature for the hydrocarbon orhydrocarbons until the mass of the intermediate body has increased atleast 3% thereby producing a work piece in the form of a rigidcarbonaceous skeleton; and thereafter thermochemically treating the workpiece in a medium of a gaseous halogen to produce the porous carbonarticle having nanopores of a size X.
 2. The method according to claim1, wherein the carbide powders are chosen in dependence of desireddistribution of nanopores by sizes using the relationship:ψ_(i)=_(Ki)φ_(i) /ΣK _(i)φ_(i) where ψ_(i)—volumetric part of nanoporeswith size x_(i) in total volume of nanopores; φ_(i)—volumetric part ofi-th carbide in particle mixture; n—number of carbides;K _(i) =l−νM _(c)ρ_(ki) /M _(ki)ρ_(c) where M_(c)—molecular mass ofcarbon, g/mole; M_(ki)—molecular mass of i-th carbide, g/mole;ρ_(ki)—density of i-th carbide, g/ccm; ρ_(c)—density of carbon, g/ccm;N—number of carbon atoms in carbide molecule.
 3. The method according toclaim 1, wherein the intermediate body has a porosity of 30–70 vol %. 4.The method according to claim 1, wherein the treatment in a medium ofgaseous hydrocarbon or hydrocarbon mixtures is carried out until themass of the intermediate body has changed according to the followingrelationship:Δm=Q(ε₀ −V _(tr))/(1−ε₀) where Δm—relative change of intermediate bodymass, g/g; ε₀—porosity of intermediate body, vol %; V_(tr)—predeterminedvolumetric content of transport pores, vol %;Q=ρ _(c)/ρ_(mix) where ρ_(c)=density of carbon, g/ccm; ρ_(mix)=densityof carbides mixture, g/ccm.
 5. The method according to claim 1, whereinthe intermediate body is formed by pressing.
 6. The method according toclaim 1, wherein the intermediate body is formed by slip casting, tapecasting or slurry casting.
 7. The method according to claim 1, whereinthe mixture of hydrocarbons comprises a natural gas.
 8. The methodaccording to claim 7, wherein the treating in hydrocarbon medium iscarried out at 750–950° C.
 9. The method according to claim 1, whereinat least one of the hydrocarbons used during the treatment of theintermediate body in hydrocarbons medium is selected from the groupconsisting of acetylene, methane, ethane, propane, pentane, hexane,benzene and their derivatives.
 10. The method according to claim 9,wherein the treating in hydrocarbon medium is carried out at 550–1200°C.
 11. The method according to claim 1, wherein the particles of carbideor carbides of which the intermediate body is formed are arrangeduniformly throughout its volume.
 12. The method according to claim 1,wherein the particles of carbide or carbides of which the intermediatebody is formed are arranged nonuniformly throughout its volume.
 13. Themethod according to claim 1, wherein the gaseous halogen compriseschlorine.
 14. The method according to claim 1, wherein thethermochemical treatment of the workpiece is carried out at 350–1200° C.15. The method according to claim 14, wherein the thermochemicaltreatment is carried out at 500–1100° C.
 16. The method according toclaim 3, wherein the intermediate body has a porosity of 35–50 vol %.17. A method for producing a porous carbon article comprising the stepsof: selecting powders of at least one carbide of an element selectedfrom the group consisting of Group III, IV, V and VI of Mendeleyv'sPeriodic System, the at least one carbide having physical and chemicalconstants to obtain a porous carbon article having a desirednanoporosity by calculating using the relationship:X=Z*(1−R)/R where X=specified size of desired nanopores and X≦10 nm, nm;Z=0.65–0.75 nm;R=νM _(c)=ρ_(k) /M _(k)ρ_(c) where M_(c)—molecular mass of carbon,g/mole; M_(k)—molecular mass of the selected carbide, g/mole;ρ_(k)—density of the selected carbide, g/ccm; ρ_(c)—density of carbon,g/ccm; ν—number of carbon atoms in carbide molecule; forming anintermediate body with transport pores having a size larger than 100 nmby shaping the selected powders; heat treating the intermediate body ina medium of gaseous hydrocarbon or hydrocarbon mixtures at a temperatureexceeding the decomposition temperature for the hydrocarbon orhydrocarbons until the mass of the intermediate body has increased atleast 3% thereby producing a workpiece in the form of a rigidcarbonaceous skeleton; and thereafter thermochemically treating the workpiece in a medium of a gaseous halogen to produce the porous carbonarticle having nanopores of a size X, and wherein the intermediate bodyhas a porosity determined with the following relationship:ε₀=(1−ν_(np) /ΣK _(i)φ_(i))*100 ε₀ porosity of intermediate body vol %;where φ_(i)—volumetric part of i-th carbide in particle mixture;ν_(np)—predetermined volumetric part of nanopores in final article;K _(i)=1−νM _(c)ν_(ki) /M _(ki)ν_(c) where M_(c)—molecular mass ofcarbon, g/mole; M_(k)—molecular mass of i-th carbide, g/mole;ρ_(ki)—density of i-th carbide, g/ccm; ρ_(c)—density of carbon, g/ccm;ν—number of carbon atoms in carbide molecule.